The present invention relates, in general, to a motility stimulating protein and compositions comprising the same. In particular, the present invention relates to a purified form of the protein and peptides thereof, for example, autotaxin (herein alternative referred to as xe2x80x9cATXxe2x80x9d); a DNA segment encoding autotaxin; recombinant DNA molecules containing the DNA segment; cells containing the recombinant DNA molecule; a method of producing autotaxin; antibodies to autotaxin; and methods of cancer diagnosis and therapy using the above referenced protein or peptides thereof and DNA segments.
Cell motility plays an important role in embryonic events, adult tissue remodeling, wound healing, angiogenesis, immune defense, and metastasis of tumor cells (Singer, 1986). In normal physiologic processes, motility is tightly regulated. On the other hand, tumor cell motility may be aberrantly regulated or autoregulated. Tumor cells can respond in a motile fashion to a variety of agents. These include host-derived factors such as scatter factor (Rosen, et al., 1989) and growth factors (Kahan, et al., 1987; Stracke, et al.; Tamm, et al., 1989; Wang, et al. 1990; and Jouanneau, et al. 1991), components of the extracellular matrix (McCarthy, et al. 1984), and tumor-secreted or autocrine factors (Liotta, et al. 1988; Ruff, et al. 1985; Atnip, et al. 1987; Ohnishi, et al. 1990; Silletti, et al. 1991; and Watanabe, et al. 1991).
Many types of host-derived soluble factors act in a paracrine fashion to stimulate cell locomotion. Motility-stimulating proteins called xe2x80x9cscatter factorsxe2x80x9d have been identified which are produced by embryonic fibroblasts and by smooth muscle cells (Stoker, et al. 1987). Scatter factors stimulate random and directed motility by epithelial cells, keratinocytes, vascular endothelial cells and carcinoma cells (Stoker, et al. 1987; Rosen, et al. 1990; and Weidner, et al. 1990), but not fibroblasts. In addition, a number of host-secreted growth factors have been demonstrated to stimulate motility in tumor cells, including nerve growth factor (Kahan, et al. 1987) insulin-like growth factor-I (Stracke, et al. 1988), interleukin-6 (Tamm, et al. 1989), interleukin-8 (Wang, et al. 1990), and acidic fibroblast growth factor (Jouanneau, et al. 1991). These paracrine factors may influence xe2x80x9chomingxe2x80x9d or the directionality of tumor cell motility.
In contrast to these host-derived factors, many types of tumor cells have been found to produce proteins termed xe2x80x9cautocrine motility factorsxe2x80x9d which stimulate motility by the same tumor cells which make the factor (Liotta, et al. 1986). Autocrine motility factors are not specific for a given type of cancer cell but have a wide spectrum of activity on many types of cancer cells (Kohn, et al. 1990), with little effect on normal fibroblasts or leukocytes.
Autocrine motility factors identified to date act through cell-surface receptors (Stracke, et al. 1987; Nabi, et al. 1990; Watanabe, et al. 1991) resulting in pseudopodial protrusion (Guirguis, et al. 1987) leading to both random and directed migration (Liotta, et al. 1986; Atnip, et al. 1987; Ohnishi, et al. 1990).
Prior studies of human A2058 melanoma cells have demonstrated that these cells are a particularly rich source of autocrine motility factors. An autocrine motility factor with a molecular mass of approximately 60 kDa has been previously isolated from the conditioned media of these cells. (Liotta, et al. 1986). Similar tumor cells derived or induced factors with the same molecular weight have subsequently been reported and purified by several investigators (Atnip, et al. 1987; Schnor, et al. 1988; Ohnishi, et al. 1990; Silletti, et al. 1991; Watanabe et al. 1990). Such factors are thought to play a key role in tumor cell invasion.
Most of the motility factors identified to date have not been purified to homogeneity and have not been sequenced. The novel tumor motility factor of the present invention, named herein as autotaxin (xe2x80x9cATXxe2x80x9d), has been purified and verified to be a homogeneous sample by two-dimensional gel electrophoresis. The protein of the present invention is unique from any previously identified or purified motility factor. The molecular size of ATX is about 125 kilo Daltons (xe2x80x9ckDaxe2x80x9d) and it has an isoelectric point of approximately 7.7. ATX stimulates both random and directed migration of human A2058 melanoma cells at picomolar concentrations. The activity of the ATX factor is completely sensitive to inhibition by pertussis toxin. No significant homology has been found to exist between the protein of the invention and any mammalian protein including previous factors known to stimulate cell motility.
There is a great clinical need to predict the aggressiveness of a patient""s individual tumor, to predict the local recurrence of treated tumors and to identify patients at high risk for development of invasive tumors. The present invention provides a functional marker which is functionally related to the invasive potential of human cancer. The invention further provides an assay for this secreted marker in body fluids, or in tissues. The assay of the invention can be used in the detection, diagnosis, and treatment of human malignancies and other inflammatory, fibrotic, infectious or healing disorders.
The present invention relates, generally, to a motility stimulating protein and corresponding peptides thereof, and to a DNA segment encoding same. A human cDNA clone encoding a tumor cell motility-stimulating protein, herein referred to as autotaxin or xe2x80x9cATXxe2x80x9d, reveals that this protein is an ecto/exoenzyme with significant homology to the plasma cell membrane differentiation antigen PC-1. ATX is a 125 kDa glycoprotein, previously isolated from a human melanoma cell line (A2058), which elicits chemotactic and chemokinetic responses at picomolar to nanomolar concentrations.
It is a specific object of the present invention to provide autotaxin and peptide fragments thereof.
It is a further object of the present invention to provide a DNA segment that encodes autotaxin and a recombinant DNA molecule comprising same. It is a further object of the present invention to provide a cell that contains such a recombinant molecule and a method of producing autotaxin using that cell.
Another object of the present invention is the identification of a transmembrane domain of the human liver autotaxin protein and its apparent absence in tumorous forms of autotaxin. The tumorous form of autotaxin appears to be a secreted protein. The present invention relates to utilization of the different sites of localization for diagnosis and prognosis of the stages of tumor progression. Further, the invention relates to treatment methods, designed to advantageously block the secreted form of autotaxin activity while having little effect on the membrane-bound form of autotaxin.
Yet another object of the present invention relates to the identification of a highly variable region within the autotaxin gene, called a xe2x80x9chot spotxe2x80x9d. The variations in sequence apparently result in mutations, insertions, deletions and premature termination of translation. The present invention relates to manipulating this region so as to alter the activity of the protein. Further, the hot spot can serve as a marker in tumor diagnosis differentiating between different forms of the autotaxin protein.
It is yet another object of the present invention to provide a method of purifying autotaxin.
It is a further object of the present invention to provide cloned DNA segments encoding autotaxin and fragments thereof. The cDNA encoding the entire autotaxin protein contains 3251 base pairs, and has an MRNA size of approximately 3.3 kb. The full-length deduced amino acid sequence of autotaxin comprises a protein of 915 amino acids. Database analysis of the ATX sequence revealed a 45% amino acid identity (including 30 out of 33 cysteines) with PC-1, a pyrophosphatase/type I phosphodiesterase expressed on the surface of activated B cells and plasma cells. ATX, like PC-1, was found to hydrolyze the type I phosphodiesterase substrate p-nitrophenyl thymidine-5xe2x80x2 monophosphate. Autotaxin now defines a novel motility-regulating function for this class of ecto/exo-enzymes.
Further objects and advantages of the present invention will be clear from the description that follows.